This invention relates to the measurement and evaluation of surface flatness, particularly with respect to concrete floors utilized in building construction.
The measurement of floor flatness or levelness is generally accomplished today by use of relatively long straight edges or point-to-point measurements made with transits and story rods or laser projectors and sensors. Only by use of transits or laser projectors, measurement data is produced from which surface profile plots may be drawn. However, the collection of elevation data by use of such equipment is slow and of questionable accuracy. For example, elevation differences between adjacent point locations of less than 1/16 of an inch are very expensive to measure with such equipment.
Because of the inability of existing equipment to provide floor surface measurements in a simple, accurate and standardized manner, considerable confusion exists in the construction industry with regard to the proper interpretation of flatness/levelness specifications and the establishment of realistic and enforceable tolerance values with respect to flatness or levelness. Accordingly, an important object of the present invention is to provide a relatively simple, rapid and standardized means for measuring and recording the surface profile of a floor surface with sufficient accuracy and repeatability to accommodate enforceable standards with respect to floor flatness/levelness.
Empirical studies with respect to commercial concrete floor surfaces indicate that such floor surfaces exhibit surface undulations having a small amplitude to wavelength ratio with a maximum wave amplitude of less than one-half inch and a wavelength (i.e. distance between high or low spots) within a limited range. Such dimensional characteristics of the surface undulations result from the physical dimensions of existing equipment utilized to place and finish concrete floor surfaces. It therefore follows that any proper evaluation of surface flatness or levelness requires plotting of a surface profile from measurement data obtained at points on the surface separated by less than one quarter the characteristic wave length of the surface undulations. The use of such small spacing between measurement points insures that the plotted profile will reveal all undulations in the surface. As hereinbefore indicated, the measurement of elevations at such closely spaced points heretofore involved a slow measurement procedure producing measurement data of questionable accuracy. It is, therefore, another important object of the present invention to provide apparatus and method by means of which rapid and accurate elevation measurements at closely spaced points on a surface may be made in order to plot a surface profile from which accurate and reliable evaluation of surfaces may be made.